Phylogeny of Gremmeniella spp. based on sequences of the 5.8S rDNA and internal transcribed spacer region

Sequences in the 5.8S rDNA and internal transcribed spacer region were obtained for taxa belonging to Gremmeniella spp., and a phylogenetic analysis was carried out using parsimony and distance methods. A set of hypotheses concerning evolutionary relationships between members of that genus was tested. The hypothesis that all members of Gremmeniella abietina var. abietina are closely related was rejected. It appears that the Asian race is quite divergent from the European and North American races, but could be more closely related to G. abietina var. balsamea. The phylogeny was consistent with host specificity: members of G. abietina var. abietina generally do not infect Abies or Picea spp. but the Asian race occurs on Abies sachalinensis in Japan. The hypothesis that host specialization has created divergence within G. abietina var. balsamea was supported by our analysis because the levels of divergence between isolates originating from Picea spp. and Abies spp. were similar to those found between the North American and European races of G. abietina var. abietina. The hypothesis that greater divergence occurred between Gremmeniella abietina and Gremmeniella laricina than between G. abietina var. abietina and G. abietina var. balsamea was not supported. The level of divergence was as large between the two varieties within G. abietina as between the two species G. abietina and G. laricina. These results indicate that similar taxonomic levels should be applied to these three taxa.